Imported feed could riddle Med fish with viruses

A report by the group showed that large quantities of imported feed-fish were used for European tuna farming, potentially bringing alien diseases into the Mediterranean that could infiltrate and damage local ecosystems.

During their captivity, which lasts around six months, tunas are fed around 225,000 tonnes of imported frozen, untreated fish from regions such as West Africa, the North Atlantic, and North and South America.

This is more than the Mediterranean’s annual catch of sardines.

“Dumping of imported feed-fish into the Mediterranean tuna farms must stop immediately,” WWF fisheries expert Dr Sergi Tudela warned. “It threatens both the health of local fish populations and ecosystems, as well as the livelihoods of fishermen that rely on them.”

With Spain, Malta, Italy, Greece and Cyprus accounting for nearly three quarters of officially declared tuna farming activity in the Mediterranean, the problem is mostly European and must therefore be regulated by the Commission, according to the report.

In a similar case in the 1990s, alien feed-fish imports dumped in Australian tuna farms from other regions ended up causing viral epidemics that affected 5,000km of coastline and killed 75% of the country’s adult sardine population.

“The risk of disease transmission is very high,” fish pathologist with Western Australia’s Department of Fisheries Dr Brian Jones said. “Most fish viruses rely either on direct feeding or proximity to spread, and we set up a classic transmission experiment every time we feed sardines to tuna.”

Dr Tudela added that it was virtually impossible to analyse frozen feed-fish imports regularly to ensure that they were free from harmful viruses.

“The only solution is to have a total ban of such practices,” he pointed out. “In Denmark use of feed-fish in saltwater aquaculture has been banned since 1985 – the EU should take the same approach to Mediterranean tuna farms.”

By Jane Kettle